I really hope going Morton today reinforces that there is no chance we do something stupid in thinking his "experience" puts him ahead of SS in the rotation.
My take on this was simply we want to have SS available for the 1st round and take our chances on winning today without needing him. If SS goes today vs. tomorrow either way he isn't available for the WC round - so there is really nothing you gain by pitching Shelly a day earlier. Whereas you potentially gained not needing to pitch SS(with Morton going today), and thus having SS available in 1st round as needed.
Either way, even if SS is used tomorrow, he still would be on regular rest to start an NLDS game one. We just lose the option of him being available in a WC game three all hands on deck.